This relates generally to analog-to-digital converters, and more specifically, to massively parallel analog-to-digital converters. Massively parallel analog-to-digital converters may be included within image sensors.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Image sensors (sometimes referred to as imagers) may be formed from a two-dimensional array of image sensing pixels. The array of image sensing pixels are typically arranged in pixel rows and columns. Each pixel includes a photosensitive layer that receives incident photons (light) and converts the photons into electrical charge. Column sensing circuitry is typically coupled to each pixel column for reading out image signals from the image pixels.
Conventional image sensors often include analog-to-digital conversion circuitry to convert analog signals from the image pixels to digital signals. Amplifiers may be included to amplify the analog signals from the image pixels prior to analog-to-digital conversion. Amplifiers have an associated gain that determines the amount by which the analog signals are multiplied. However, conventional image sensors can have uncertain or inconsistent amplifier gains that can lead to inaccuracies in the analog-to-digital conversion.
It would therefore be desirable to be able to provide improved analog-to-digital converters for converting signals amplified by an amplifier.